CPCS Working Near Services & Site Hazards 2 — Questions and Answers
Question 1: What is 'flashover' in the context of overhead power lines?
- Electricity arcing from a power line to nearby conductive objects without direct contact — potentially fatal (Correct answer)
- A fire caused by plant striking a power pole
- The reflection of sunlight from power lines into the operator's cab
- The noise made by plant passing under high-voltage lines
Correct answer: Electricity arcing from a power line to nearby conductive objects without direct contact — potentially fatal
Flashover occurs when electricity arcs from a power line to a nearby conductive object — such as a crane boom — without direct contact. It can be fatal to the operator and to persons on the ground.
Question 2: What is the minimum safe distance from a 33 kV overhead line when using construction plant?
- 6 metres or as specified by the DNO (Distribution Network Operator) (Correct answer)
- 1 metre
- The distance the crane operator considers safe
- 1.5 metres for all voltage levels
Correct answer: 6 metres or as specified by the DNO (Distribution Network Operator)
Safe distances from overhead lines depend on voltage and must be confirmed with the DNO. For 33 kV lines the minimum is typically 6 metres, but the DNO must be consulted for site-specific guidance.
Question 3: Before plant operates near overhead lines, what physical controls should be in place?
- Goal posts, height restrictors, and banksman to prevent plant approaching closer than the exclusion zone (Correct answer)
- Warning signs alone are sufficient
- The operator should rely on their own judgement of safe distance
- Only verbal briefings are needed for experienced operators
Correct answer: Goal posts, height restrictors, and banksman to prevent plant approaching closer than the exclusion zone
Physical controls including goal posts (overhead barriers) and height restrictors are required to physically prevent plant from approaching the exclusion zone, backed by a banksman to monitor proximity.
Question 4: What is the colour coding for water mains in UK underground services?
- Blue (Correct answer)
- Yellow
- Green
- Black
Correct answer: Blue
Water mains are identified by blue in the UK underground services colour coding system. Striking a water main causes flooding and can undermine ground stability.
Question 5: What is a 'permit to dig' and when is it required?
- A formal document authorising excavation work in an area with known underground services — required before any excavation near services (Correct answer)
- A permit only required for deep excavations over 2 metres
- An optional document that can be replaced by a verbal briefing
- Only required on public highways, not on private sites
Correct answer: A formal document authorising excavation work in an area with known underground services — required before any excavation near services
A permit to dig is a formal document that controls excavation in areas with underground services. It details the services present, precautions required, and authorises work to proceed. Required before excavation near any services.
Question 6: A plant operator is working near a communications cable (telephone/data). What colour identifies this type of service?
- Grey or purple (Correct answer)
- Yellow
- Blue
- Red
Correct answer: Grey or purple
Communications cables (telephone and data) are typically identified by grey or purple in the UK service identification system. Striking them causes disruption and can still present electrical hazard.
CPCS Working Near Services & Site Hazards 2
What is 'flashover' in the context of overhead power lines?